1. Field of the Invention
The present invention relates to an optical apparatus capable of preventing movable optical units from being moved by gravity in a state of being tilted from a horizontal posture.
2. Description of the Related Art
When an optical apparatus including optical units movable in an optical axis direction such as a lens unit and an iris unit is used in a state (tilted use state) where the optical axis direction is tilted with respect to a horizontal direction, an obliquely downward force caused by gravity acts on each optical unit in an obliquely downward direction, which increases a load of each actuator driving each optical unit.
Japanese Patent Laid-Open No. 58-154822 discloses an optical apparatus provided with a balancer cam inside a driving cam barrel that moves an optical unit in an optical axis direction in order to avoid a natural displacement of the optical unit due to gravity in the above-mentioned tilted use state. In the apparatus, balancing a force acting on the driving cam barrel due to a weight of the balancer cam with a force acting on the driving cam barrel from the optical unit by the gravity suppresses rotation of the driving cam barrel to prevent sliding of the optical unit.
Moreover, Japanese Patent Laid-Open No. 05-313055 discloses an optical apparatus that changes electric power (electric current value) to be applied to an actuator driving an optical unit according to a tilt angle of the optical apparatus and a movement direction of the optical unit in the tilted use state.
However, the optical apparatus disclosed in Japanese Patent Laid-Open No. 58-154822 requires the balancer cam having a weight generating a same force as the force acting on the driving cam barrel from the optical unit by the gravity, which significantly increases a weight of the entire apparatus.
Moreover, the optical apparatus disclosed in Japanese Patent Laid-Open No. 05-313055 requires increase of the electric power continuously applied to the actuator in the tilted use state in order to avoid the movement of the optical unit in the obliquely downward direction due to the gravity, which increases power consumption of the actuator and an amount of heat generation. The generated heat may deform members around the actuator.